The invention relates to a fuel tank having a fuel vapor trapping device, arranged in its filler pipe for trapping fuel vapors during refuelling and comprising a tank space located above a maximum fuel fill line which space is connected to an activated carbon filter through a vapor line which has a self closing valve moveable into a first open position to allow connection to the tank space.
A fuel tank having a trapping device of this general kind is known (German Offenlegungsschrift No. 3,605,708). The control valve of this trapping device ensures that there is no connection between the activated carbon filter and the fuel tank when the filler pipe is closed and that a desired positive pressure is maintained in the fuel tank, given appropriate design of a ventilating device. In addition, it is ensured that no fuel can escape into the open from the fuel tank via the activated carbon filter in the event of the fuel tank being in an inclined or upside down position due to an accident.
For refuelling, the control valve of this trapping device is to be brought into its open position so that the fuel vapors, which are composed of hydrocarbons and therefore highly injurious to health, cannot flow out of the fuel tank into the atmosphere but can flow off into the activated carbon filter.
In this arrangement, the fuel dispenser filler nozzle which is Placed into the filler pipe for filling the fuel tank also serves indirectly to open the control valve. In order to avoid the possibility of relatively large quantities of fuel vapors flowing out into the open as the dispenser filler nozzle is being introduced, a guide channel, which restricts the filler pipe and receives the fuel dispenser filler nozzle in a sealing fashion, is provided inside the filler pipe. The inner end of the guide channel is held closed in gastight fashion by means of a self-closing closure flap when the fuel dispenser has been removed from the filler pipe.
In this arrangement, the control valve forms a self-contained constructional unit. The valve element of this unit can be moved mechanically into an open throughflow position by the closure flap as it is pivoted into its open position by means of the fuel dispenser filler nozzle.
For this purpose, the closure flap is equipped with a forked operating lever. The fork legs come to rest against a head of a valve element shaft of the control valve when the closure flap is pivoted into its open position to thereby displace the valve element against the action of a restoring force into its open through-flow position. This establishes a connection of the fuel tank with the activated carbon filter. Fuel vapors can thereby flow off during the refuelling procedure without escaping from the filler pipe.
For the control valve, this known construction requires a valve mechanism with a specially designed valve element which can be operated by the closure flap. This likewise requires a special design, as well as two vapor lines located outside the filler pipe and connected to the control valve and filler pipe, one of which lines is to be guided away from the fuel tank and the other is to be connected to the activated carbon filter.
It is the object of the present invention to simplify both the design and installation of the control valve and the means required for its actuation as well as to design them in such a way that only a single line needs to be installed outside the filler pipe. This line being one connecting the control valve to the activated carbon filter.
According to the invention, this object is achieved, by having the closure flap act as the valve mechanism to both seal off the inlet fuel opening as well as seal off the passage from the fuel tank space into the activated carbon filter.
Thus in the design according to the invention, a special valve element is dispensed with because the closure flap takes over its function. In this arrangement, an opening to be closed by the closure flap forms the control valve seat situated inside the filler pipe, so that the filler pipe is simultaneously given the function of a line for connecting the tank space accommodating the fuel vapors to the control valve.
An embodiment of the invention offers the possibility of combining the components necessary for discharging fuel vapors into the activated carbon filter to form a single constructional unit which can be easily inserted into the filler pipe by having a housing with a guide channel for sealing enclosing the fuel nozzle with an end opening adjacent a second end opening leading to the carbon filler and having the flap valve close both end openings simultaneously.
At the same time, the first opening is alligned with the fuel nozzle and is spaced from the seal for the fuel nozzle. Also, the opening of the guide channel which restricts the filler pipe and receives the fuel dispenser filler nozzle, is to be closed by the closure flap and simultaneously also forms the valve seat of the control valve to the carbon filter.
In one embodiment of the invention, the valve seat of the control valve is formed by an additional end wall opening of a housing which can be inserted into the filler pipe, with the advantage that a valve space, which is independent of the guide channel and is to be connected directly to the activated carbon filter, can be provided directly behind this end wall opening.
A further advantage is obtained when the closure flap is in the closing position, i.e. while the control valve is closed. Here balanced pressure conditions prevail between the fuel tank and the guide channel due to a further opening in the housing, and accordingly the closure flap can easily be pivoted into its open position. In the case of a disproportionately large pressure rise in the fuel tank, caused for example, by fire, the positive pressure can be held at an uncritical level by the filler pipe cap, which is customarily designed as a pressure-relief valve.
A further advantage of the invention arises when the pressure balance between the fuel tank and the guide channel is brought about only when a certain positive pressure is reached. This ensures that no fuel can run out, for example during cornering, if no-one has remembered to close the filler pipe correctly after refuelling has been carried out. In addition, it is thereby ensured that when the filler pipe is opened, it is not possible for fuel either to escape in the form of vapor or slosh out of the pipe orifice.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.